With a wide-range spread of Internet in recent years, an electronic business manage system employing a computer and a network has taken root as a business foundation or a social infrastructure, and mission criticality with a high level is required for an Internet related system. For this, as a rule, a scheme is carried out for incorporating such a redundant configuration of making a switchover to a preliminary resource without suspending the business even at the time of occurrence of a failure.
So as to provide redundancy, there exists the technique of internally dualizing the device to set one thereof for a active device and the other for a standby device, thereby to make provision for a component-level failure within the device, constituting a redundant group from a plurality of the devices for a purpose of making provision for a failure of a device unit such as a power failure in addition hereto, and assuming that one of them is an active resource and the others are a standby resource. However, in this moment, this device group has to be virtualized so that it appears to be a single device from a view of a user who uses it and receive a service. As one technique, a dedicated protocol for redundancy is generally used for inter-device redundancy. For example, with a router described in FIG. 20, internal dualization 4011 is pre-set for resources 401 and 402 inside a router 405, and a protocol for redundancy among a plurality of routers described in Non-patent document 1, i.e. VRRP (Virtual Router Redundancy Protocol) V10, is employed to provide redundancy between the devices, thereby making it possible to assume the foregoing redundant configuration. In this moment, one virtual router 407 appears to be existent from a view of a user who uses this router.
Further, dualizing the device internally against a component failure within it, which requires only a switchover in the inside without changing a physical device itself, is more desirable than switching over the device itself as a failure recovery technique; however providing a large number of dualized devices for a purpose of redundancy gives rise to dualization of the standby resource, which means that a resource utilization efficiency is 50% at maximum with active:standby=1:1, and thus, it is difficult to incorporate such a configuration of N+1 redundancy in which one redundant resource is shared by N. Further, putting discrete devices side by side consumes a space, and is wasteful. Thereupon, instead of employing discrete devices having a function fixed, modularized unit resources are mounted onto a unified platform to perform a necessary setting (hereinafter, referred to as a service), whereby necessary devices are virtually formed without restraint, which makes it possible to curtail a space that is consumed, to enhance an efficiency of resource utilization, to enhance a flexibility of a utilization mode, or the like. Further, by employing a stacking technology, it is also possible to cause the discrete devices to sit astride a plurality of shelves that are physically separate, thereby to virtualize them as resources on one platform. As compared with the discrete devices having various settings such as the setting of hardware performed already at the time of delivery, the devices in the foregoing service that requires the setting of hardware etc. necessitates the more complicated management business such as the setting of the device. With the technology of virtualizing the resource, however, a scheme for facilitating the setting for constituting the virtual device is carried by providing a virtual resource pool, registering the physical resources into the corresponding virtual resource pool based upon properties, for example, a kind and a performance, and concealing information that is not necessary is concealed in selecting the resource. For example, in FIG. 25, a physical resource 906 having a shelf 904 and unit physical resources 905 is classified according to attributes such as its performance and kind, and registered into a virtualized pool 901 after concealing information that is unnecessary for a resource user, for example, a physical arrangement. The resource user does not directly set information of the physical resource 906, but sets it based upon information of the virtual resource within the virtual resource pool, and management software manages a relation between a virtual resource 903 and a unit physical resource 905, or the like, whereby the user does not have to alter the setting, but it is enough that it alters only related information that the management software keeps also in a case where an alteration to the physical resources that is accompanied by an alteration to the system is made, or the like.
By logically setting the virtualized resource, in dualizing the virtual resource (hereinafter, referred to as a component) constituting the above-mentioned service, it is possible for the components within a plurality of the services incorporating the redundant configuration to share, for example, one virtual resource, thus enabling a resource utilization efficiency to be enhanced. For this, for example, in a case where routers, each of which has the component dualized inside it as mentioned above, are set as a certain service, and yet a plurality of the routers assume the redundant configuration, it is also possible to logically set “standby” components of respective router as a plurality of the separates devices while sharing a certain resource, to realize intra-device dualization while realizing an effective utilization of the resource, or the like. Further, the redundant configuration can be incorporated with the external redundancy protocol such as the VRRP as inter-device dualization.
Further, as a redundant configuration, there exist, for example, configurations of 2N redundancy, N+M redundancy, and N-Way redundancy as specified by a redundant framework of AIS (Application Interface Specification) described in Non-patent document 2. In each of FIG. 21 to FIG. 23, one example of the redundant configuration is shown. A service group is defined as an aggregation for providing a certain service, in which a service instance, a node, and a service unit exist. The so-called service instance is a logical entity of the service that should be provided, the node is a logical entity signifying a gathering of the physical resources from which some resource is provided, and the service unit is a logical entity existing on the above node. A plurality of the service units, each of which becomes an “active” one or a “standby” one depending upon the redundant configuration that is employed, are caused to pre-relate to the above service instances, which designates the “standby” service unit for a failure recovery when the “active” service unit becomes useless due to a failure etc. For example, FIG. 21 shows an example of the 2N (N=1) redundancy setting on discrete nodes in which one service instance 502 exists for a service group 501, a service unit 503 on a node 505 and a service unit 504 on a node 506 are defined, respectively, and the service unit 503 has been set for an “active” one and the service unit 504 for a “standby” one. Each of FIG. 22 and FIG. 23 shows an example of a configuration of 2N (N=3) redundancy.
Herein, various redundant configurations can be designated depending upon which redundant configuration is incorporated for the service units, and which node each of them is arranged for. The node, which signifies an aggregation of the physical resources, shares a risk. For this, when a node failure occurs, the service unit set thereon becomes useless.
Non-patent document 1: RFC2338
Non-patent document 2: SAI-AIS-A.01.01, P67